In-vitro activity of meropenem, a new carbapenem, against multiresistant Pseudomonas aeruginosa compared with that of other antipseudomonal antimicrobials.

The novel carbapenem meropenem, which is stable to dehydropeptadase action, was studied in vitro against 173 nosocomial isolates of Pseudomonas aeruginosa derived from pus, expectorated sputum, bronchial secretions, urine or blood of infected patients. Susceptibilities to meropenem, imipenem, ceftazidime, cefotaxime, piperacillin, gentamicin, amikacin and ciprofloxacin were determined by the agar dilution technique with an inoculum of 10(4) cfu/spot. The proportion of sensitive isolates with MICs below the breakpoint was highest for meropenem (91% less than or equal to 8 mg/l); the proportion of sensitive isolates for the remaining antibacterials was as follows: ciprofloxacin 87% less than or equal to 2 mg/l; imipenem 85% less than or equal to 8 mg/l; ceftazidime 77.5% less than or equal to 16 mg/l; piperacillin 60% less than or equal to 64 mg/l; amikacin 44% less than or equal to 8 mg/l; gentamicin 34% less than or equal to 4 mg/l and cefotaxime 15% less than or equal to 16 mg/l. Strains moderately resistant to imipenem (MIC 16-32 mg/l) were mostly sensitive to meropenem, but highly resistant strains (MIC 128-256 mg/l) were invariably resistant (MIC greater than 128 mg/l) to the new carbapenem.